CONTROLLING LEGIO!NELIA IN HOSPITAL WATERSYSTEMS: EXPERIENCE WITH THE SUPERHEAT-AND-FLUSH METHOD AND COPPER-SaVER IONIZATION

ORJECI1VE: To evaluate the effect of copper-silver ionization on Legionella colonization and nosocomial legionnaires' disease and to compare the efficacy of metal ions versus the superheat-and-tlush method of disinfection. DESIGN: Prospective determination over a 36-month period of copper and silver ion concentrations in the recirculating hotwater system, Legionella colonization of the hospital water distribution system, and cases of nosocomial legionnaires' disease. Retrospective comparison of results with the previous 13 years, during which the superheat-and-tlush method was used. SFmNG: The Pittsburgh Veterans' Affairs Health Care System (University Drive Division) acute-care hospital. 1NrnRVENl10N: Three copper-silver ionization systemswere installed on the hot-water distribution system in November 1994. RESULTS: The average number of cases of legionnaires' disease per year and the percentage of distal sites positive for Legionella pneumoPhila for the superheat-and-flush method versus the copper-silver ionization method was six cases with 15% positivity versus two cases with 4% positivity, respectively. The reduction in Legionella colonization after copper-silver ionization was significant (P<.05) compared to the superheat and flush. Mean copper and silver ion concentrations (rng/L) were 0.29 and 0.054 from hot-water tanks, and 0.17 and 0.04 from distal outlets, respectively. CONCWSIONS: We conclude that a properly maintained and monitored copper-silver ionization system was more effective than the superheat-and-flush method for reducing the recovery of Legionella from the hospital water distribution system (Infect Control Hosp EpidemioI1998;19:91l-914). versus superheat-and-flush, for controlling Legionella colonization and nosocomial legionnaires' disease.